Conventionally, in a vehicle having an internal combustion engine (engine) as a source of driving force, an automated manual transmission (hereinafter referred to as an AMT) has been known, wherein actuators are provided in an existing manual transmission for automatically operating a series of gear shifting operations such as clutch engagement/disengagement, gear shifting, gear selecting, in response to an intension or request of an operator of the vehicle or depending on a vehicle running state. In clutch operation of the AMT, the clutch is controlled by converting the clutch torque required depending on the vehicle performance characteristics into a clutch actuator operating amount (operating amount of the clutch actuator). Upon shipping of the vehicle, the relationship between the clutch torque and the clutch actuator operating amount is statically obtained based on a cushioning performance of the clutch disc or the like. However, under a vehicle actually running state, other dynamic variable factors largely influence on the relationship between the clutch torque and the clutch actuator operating amount. Such influencing dynamic variable factors are for example, abrasion of clutch facing, changes of the coefficient of friction (μ) due to generated heat and the aged deterioration.
As the relationship between the clutch torque and the clutch actuator operating amount varies, an intended clutch engagement/disengagement operation upon gear shifting cannot be carried out timely in case of AMT vehicle. In more detail, when the clutch disengaged state exceeds the intended time, it may occur a situation that the engine torque is not transmitted to the vehicle wheels during the clutch disengaged operation, the operator of the vehicle feels stall of the vehicle. Further, when the clutch disengaged operation continues for a longer period of time, the engine which receives no load will excessively revolve, which may lead to an excess shifting shock due to a great difference between the engine rpm (revolution per minute) and input shaft rpm of the transmission upon clutch engagement operation. Accordingly, a technology has been proposed in, for example, a Patent Document 1 that the clutch torque map which determines the relationship between the clutch torque and the clutch actuator operating amount is corrected by learning the relationship therebetween properly when appropriated. According to the proposed technology in the Patent Document 1, the learning is performed at the time of vehicle starting where a clutch engagement/disengagement operation is carried out. When the vehicle starts, the rpm of the input shaft of the transmission is approximately zero (0) and accordingly, an always stable relationship between the clutch torque and the clutch actuator operating amount can be obtained. The relationship is corrected based on the obtained data to suitably set the clutch disengagement time to avoid stalling feeling for the operator of the vehicle and shifting shock due to the excessive increase of engine rpm.